Bovine somatotropin increases embryonic development in superovulated cows and improves post-transfer pregnancy rates when given to lactating recipient cows

Growth hormone in fertility and infertility: Mechanisms of action and clinical applications

Secreted by the anterior pituitary gland, growth hormone (GH) is a peptide that plays a critical role in regulating cell growth, development, and metabolism in multiple targeted tissues. Studies have shown that GH and its functional receptor are also expressed in the female reproductive system, including the ovaries and uterus. The experimental data suggest putative roles for GH and insulin-like growth factor 1 (IGF-1, induced by GH activity) signaling in the direct control of multiple reproductive functions, including activation of primordial follicles, folliculogenesis, ovarian steroidogenesis, oocyte maturation, and embryo implantation. In addition, GH enhances granulosa cell responsiveness to gonadotropin by upregulating the expression of gonadotropin receptors (follicle-stimulating hormone receptor and luteinizing hormone receptor), indicating crosstalk between this ovarian regulator and the endocrine signaling system. Notably, natural gene mutation of GH and the age-related decline in GH levels may have a detrimental effect on female reproductive function, leading to several reproductive pathologies, such as diminished ovarian reserve, poor ovarian response during assisted reproductive technology (ART), and implantation failure. Association studies using clinical samples showed that mature GH peptide is present in human follicular fluid, and the concentration of GH in this fluid is positively correlated with oocyte quality and the subsequent embryo morphology and cleavage rate. Furthermore, the results obtained from animal experiments and human samples indicate that supplementation with GH in the in vitro culture system increases steroid hormone production, prevents cell apoptosis, and enhances oocyte maturation and embryo quality. The uterine endometrium is another GH target site, as GH promotes endometrial receptivity and pregnancy by facilitating the implantation process, and the targeted depletion of GH receptors in mice results in fewer uterine implantation sites. Although still controversial, the administration of GH during ovarian stimulation alleviates age-related decreases in ART efficiency, including the number of oocytes retrieved, fertilization rate, embryo quality, implantation rate, pregnancy rate, and live birth rate, especially in patients with poor ovarian response and recurrent implantation failure.

The incompletely fulfilled promise of embryo transfer in cattle-why aren't pregnancy rates greater and what can we do about it?

Typically, bovine embryos are transferred into recipient females about day 7 after estrus or anticipated ovulation, when the embryo has reached the blastocyst stage of development. All the biological and technical causes for failure of a female to produce a blastocyst 7 d after natural or artificial insemination (AI) are avoided when a blastocyst-stage embryo is transferred into the female. It is reasonable to expect, therefore, that pregnancy success would be higher for embryo transfer (ET) recipients than for inseminated females. This expectation is not usually met unless the recipient is exposed to heat stress or is classified as a repeat-breeder female. Rather, pregnancy success is generally similar for ET and AI. The implication is that either one or more of the technical aspects of ET have not yet been optimized or that underlying female fertility that causes an embryo to die before day 7 also causes it to die later in pregnancy. Improvements in pregnancy success after ET will depend upon making a better embryo, improving uterine receptivity, and forging new tools for production and transfer of embryos. Key to accelerating progress in improving pregnancy rates will be the identification of phenotypes or phenomes that allow the prediction of embryo competence for survival and maternal capacity to support embryonic development.

Influência da somatotropina recombinante bovina no desenvolvimento folicular e na coleta de embriões em éguas

RESUMO Dez éguas, sem raça definida, foram submetidas a avaliações ultrassonográficas durante o intervalo interovulatório, avaliando-se folículos ≥ 5mm. Cinco éguas foram tratadas com 500mg de r-bST no primeiro e no 14º dia pós-ovulação (grupo GT), e as demais com soro fisiológico (grupo GC). Quando o folículo dominante atingiu diâmetro ≥ 40mm, foram induzidas com hCG e inseminadas 24 horas após, sendo submetidas à coleta de embrião seis dias após a ovulação. Os dados foram agrupados de acordo com o diâmetro do folículo dominante nas fases de emergência, divergência, dominância, pré-ovulatória, indução, inseminação e ovulação. Todas as éguas foram usadas duas vezes, no mesmo grupo. O GT apresentou crescimento folicular precoce para as fases de emergência, divergência, dominância e pré-ovulatória, assim como para o seu maior folículo subordinado, que cresceu mais cedo. As taxas de recuperação foram de 90% (GC) e 70% (GT), em 16 estruturas coletadas, obtendo-se uma não fecundada e um blastocisto inicial para o grupo GC; os demais, no estágio de mórula, apresentaram comportamento semelhante entre os grupos. Conclui-se que a r-bST influencia a dinâmica folicular de éguas, levando a uma antecipação do desenvolvimento folicular, que pode ser utilizada para encurtar o ciclo estral.

Metabolic biomarkers, body condition, uterine inflammation and response to superovulation in lactating Holstein cows

The objective was to determine associations between response to superovulation and body condition, subclinical endometritis and circulating metabolic biomarkers [adiponectin, leptin, insulin, IGF1, tumor necrosis factor (TNF) α, interleukin (IL) 1β, IL6, and urea] in lactating dairy cows. Ten multiparous lactating Holstein cows in each body condition score (1-5; 1 emaciated; 5 obese) category (BCSC) 2.00 to < 2.50 (BCSC1), 2.50 to < 3.00 (BCSC2), 3.00 to <3.50 (BCSC3), 3.50 to <4.00 (BCSC4) and 4.00 to 5.00 (BCSC5) groups (total n = 50) were randomly selected and superovulated, timed artificially inseminated with frozen-thawed semen from three sires and embryos collected (n = 50 collections). At embryo collection, blood samples and embryo recovery fluid were collected for determination of metabolic markers and presence of subclinical endometritis (lavage technique; > 6% PMN). In total, 379 embryos were collected (average of 7.6 embryos per superovulation). Mean numbers of total ova and embryos was greater for cows in BCSC2, BCSC3 and BCSC4 groups compared with cows in BCSC1 and BCSC5 groups (P < 0.01). Total number of transferrable embryos were greater for cows in BCSC 2 and BCSC3 groups compared with cows in BCSC1, BCSC4 and BCSC5 groups (P < 0.01). Mean number of total ova and embryos and of transferrable embryos was higher for cows with 0 or 1-6% PMN compared to cows with >6% PMN (P < 0.01). In addition, there was a quadratic association between blood urea nitrogen concentrations and % transferrable embryos (r² = 0.85; P < 0.05) and between BCS and % transferrable embryos (r² = 0.73; P < 0.05). Circulating adiponectin, leptin, insulin, IGF1 and TNFα were greater in cows with moderate to good body condition compared to thin or obese cows (P < 0.05). Circulating adiponectin, leptin, IGF1 and insulin were greater in normal cows (≤6% PMNs), whereas, TNFα and IL1β and IL6 were greater in cows with subclinical endometritis (P < 0.05). In conclusion, BCS and subclinical endometrial inflammation were associated with superovulatory response and embryo quality. Further, circulating metabolic biomarkers were associated with superovulatory response and embryo quality, likely due to donor's metabolic status and uterine environment. Optimizing superovulatory responses and embryo quality in lactating dairy cows requires management of nutrition and uterine health.

Effects of recombinant bovine somatotropin on pregnancy per artificial insemination, corpus luteum cellular composition and endometrial gland morphometry in beef cattle

The aim of this research was to evaluate the effect of recombinant bovine somatotropin (bST) on pregnancy per artificial insemination (P/AI), cellular composition of the corpus luteum (CL) and endometrial gland morphometry. In Experiment 1, Nelore cows (n = 587) received a fixed-time artificial insemination (FTAI) protocol and, at insemination, received 0, 250 or 500 mg of bST subcutaneously (SC). In Experiment 2, Nelore cows (n = 243) received 0 or 500 mg of bST, SC, on D7 (D0 = day of FTAI). Blood samples were collected on D7 and D16 to measure progesterone (P4) concentrations. In Experiments 1 and 2, pregnancy diagnosis was performed 30 days after FTAI. In Experiment 3, Nelore heifers (n = 20) received a FTAI protocol, but were not inseminated, and on D0 (ovulation day), they received 0 (bST 0; n = 9) or 500 mg of bST (bST 500; n = 11), SC. The heifers were slaughtered on D15 (D0 = ovulation day), at which time the CL was evaluated for diameter, weight, a percentage of large (LLC) and small (SLC) luteal cells, and the concentration of progesterone in plasma measured. The number, perimeter and area of superficial and deep endometrial glands were evaluated. There was no difference in P/AI when bST was applied on D0 and D7. In Experiment 1, P/AI did not differ among treatments, with 59.28% (115/194), 58.38% (115/197) and 65.82% (129/196) for the bST 0, 250 and 500 treatments, respectively. In Experiment 2, P/AI did not differ between treatments, with 57.3% (71/124) and 60.5% (62/119) for the bST 0 and 500 treatments, respectively. Plasma progesterone concentrations on D16 was greater in the bST 500 (11.63 ± 0.84 ng/mL) than bST 0 (9.83 ± 0.88 ng/mL). In Experiment 3, there was no difference in ovarian diameter and weight, CL diameter, percentage of SLC, P4 concentrations and endometrial gland morphology. Heifers in the bST 500 treatment had heavier CL (3.11 ± 0.32 vs. 2.25 ± 0.20 g); however, the bST 0 treatment heifers had a greater percentage of LLC than did the bST 500 treatment (13.72 ± 1.16% vs. 8.60 ± 1.52). It was concluded that the doses of bST used in this study do not increase P/AI; however, they do cause changes in P4 concentration and the cellular composition of the CL.

Regulation of present and future development by maternal regulatory signals acting on the embryo during the morula to blastocyst transition - insights from the cow

The preimplantation embryo has a remarkable ability to execute its developmental program using regulatory information inherent within itself. Nonetheless, the uterine environment is rich in cell signaling molecules termed embryokines that act on the embryo during the morula-to-blastocyst transition, promoting blastocyst formation and programming the embryo for subsequent developmental events. Programming can not only affect developmental processes important for continuance of development in utero but also affect characteristics of the offspring during postnatal life. Given the importance of embryokines for regulation of embryonic development, it is likely that some causes of infertility involve aberrant secretion of embryokines by the uterus. Embryokines found to regulate development of the bovine embryo include insulin-like growth factor 1, colony stimulating factor 2 (CSF2), and dickkopf WNT signaling pathway inhibitor 1. Embryo responses to CSF2 exhibit sexual dimorphism, suggesting that sex-specific programming of postnatal function is caused by maternal signals acting on the embryo during the preimplantation period that regulate male embryos differently than female embryos.

Customised Oocyte Donation Enhancement and New Findings Regarding the Role of Growth Hormone

In vitro fertilisation (IVF) with donated oocytes is the most effective assisted reproduction treatment currently available; however, repeated implantation failure (RIF) can occur with this treatment. The protocol of patient preparation for IVF with donated oocytes is relatively simple and works well in most cases; however, it can fail in a minority of women, which is what occurs in RIF patients. While the probability of RIF occuring is 20–35%, it is reasonable to take adequate measures in all patients in order to avoid procedural failure. The risk of oocyte donation failure can be minimised by applying a customised oocyte donation enhancement (CODE) protocol, in which pitfalls of the standard protocol are detected and corrected in the pretreatment phase, during the patient’s uterus preparation for embryo transfer, and after the transfer. Growth hormone, recently reported to improve pregnancy outcomes in women with RIF after oocyte donation, is a possible component of the CODE protocol, but it cannot be considered a unique solution to RIF. This article reviews possible causes of RIF and places growth hormone treatment in the context of other important measures to be followed in the CODE protocol.

Effect of Growth Hormone on Uterine Receptivity in Women With Repeated Implantation Failure in an Oocyte Donation Program: A Randomized Controlled Trial

Background and Objective:

Administration of growth hormone (GH) during ovarian stimulation has been shown to improve success rates of in vitro fertilization. GH beneficial effect on oocyte quality is shown in several studies, but GH effect on uterine receptivity is not clear. To assess it, we studied whether GH administration can improve the chance of pregnancy and birth in women who experienced repeated implantation failure (RIF) using donated oocyte programs.

Design and Study Population:

A total of 105 infertile women were enrolled in the randomized controlled trial: 70 women were with a history of RIF with donated oocytes, and 35 infertile women underwent the first oocyte donation attempt. Women receiving donated oocytes were treated with progressively increasing doses of oral estradiol, followed by intravaginal progesterone after previous pituitary desensitization with gonadotropin-releasing hormone agonist. Thirty-five RIF patients were treated with GH (GH patients), whereas the rest of the 35 RIF patients (non-GH patients) and 35 first-attempt patients (positive control group) were not.

Results:

RIF patients receiving GH showed significantly thicker endometrium and higher pregnancy and live birth rates as compared with RIF patients of non-GH study group, although these rates remained somewhat lower as compared with the non-RIF patients of the positive control group. No abnormality was detected in any of the babies born.

Conclusion:

Our data of improved implantation, pregnancy, and live birth rates among infertile RIF patients treated with GH indicate that GH improves uterine receptivity.

Growth hormone co-treatment within a GnRH agonist long protocol improves implantation and pregnancy rates in patients undergoing IVF-ET

OBJECTIVE

The efficacy of growth hormone (GH) co-treatment within a GnRH agonist long regimen, in women with a normal ovarian response to controlled ovarian hyperstimulation (COH), for IVF was assessed.

METHODS

This retrospective clinical trial was performed in a private-assisted reproduction centre. The study involved 1114 patients who responded normally to high-dose gonadotropin treatment. The study group of 556 patients was given in a daily subcutaneous injection of 4.5 IU of GH co-treatment, starting from the initial day of gonadotropin treatment and lasting for 5 days. The control group of 558 patients received the same treatment protocol without the GH co-treatment. The participants were further divided into two subgroups: age ≥35 years and age <35 years. The primary endpoint of the study was IVF-ET outcomes.

RESULTS

The demographic characteristics did not significantly differ between the groups. The implantation rate (36.7 vs. 20.4 %, P < 0.05) and clinical pregnancy rate (57.3 vs. 30.1 %, P < 0.05) were significantly higher in the study group than in the control group. An analysis using a multivariate logistic regression model showed that GH was a significant factor for predicting pregnancy outcomes (OR 3.125, 95 % CI 2.441-4.000). Furthermore, for the ≥35-year-old group, the endometrial thickness was significantly greater (11.99 ± 2.21 vs. 11.62 ± 2.45, P < 0.05) in the study group than in the control group; in contrast, for the <35-year-old group, the high-quality embryo rate was significantly higher (71.7 vs. 68.3 %, P < 0.05) in the study group than in the control group.

CONCLUSION

Our study showed that co-treatment with GH in a GnRH agonist long protocol in patients who responded normally while undergoing IVF-ET could increase the implantation and pregnancy rates.

Superovulatory response and embryo development in ewes treated with two doses of bovine somatotropin

This study evaluated whether the administration of 50 and 100mg bovine somatotropin (bST) at the start of synchronization and at the time of natural mating in ewes improves the ovulation rate, embryonic development and pregnancy rate of transferred embryos. Forty-eight donors were assigned to three treatments: the bST-100 treatment (n=15) received 100mg bST at the start of synchronization and at natural mating, the bST-50 treatment (n=15) received 50mg bST on the same schedule as the previous group, and the control (n=18) did not receive any bST. Two embryos were transferred to each recipient (n=121): 35 received embryos from bST-100; 50 received embryos from bST-50, and 36 received embryos from the control. The superovulatory rate, percentage of recovered structures, cleavage rate, percentage of transferable embryos, embryo quality and development and pregnancy rate were analyzed using the GENMOD procedure of SAS. The number of corpora lutea and the cell number were analyzed using the GLM procedure of SAS. The insulin and IGF-1 concentrations were analyzed with ANOVA for repeated measures. The bST application did not affect the superovulatory rate, number of corpora lutea and recovered structures (P>0.05). The numbers of transferable embryos and embryos reaching the blastocyst were higher (P≤0.01) in the bST-50 (96.4±3.6% and 69.0±7.8%) than the bST-100 (93.0±4.5% and 27.2±38.9%) and control (87.7±5.4% and 50.4±6.4%) groups. The insulin and IGF-1 concentrations were higher (P<0.05) in the bST-treated groups, but the insulin concentration was higher (P<0.05) in the bST-100 group than in the bST-50 group. The pregnancy rate was similar (P=0.21) in ewes receiving embryos from the two treatments [bST-50, (70.0%); bST-100, (62.5%), and control, (56.6%)]. The administration of 50mg bST at the start of synchronization and at natural mating in superovulated ewes was concluded to enhance the proportion and development of transferable embryos. However, bST did not affect the pregnancy rate of transferred embryos.

Qualidade do corpo lúteo e do embrião de ovelhas Santa Inês superovuladas com FSH associado à rbST

Avaliou-se o efeito da somatotropina bovina recombinante (rbST) sobre a qualidade do corpo lúteo e do embrião e sobre a concentração de progesterona (P4), em ovelhas da raça Santa Inês doadoras de embriões. Foram utilizadas 13 doadoras, distribuídas aleatoriamente em dois grupos, G1 (n=7) e G2 (n=6). Em ambos os grupos, as doadoras foram sincronizadas com implante vaginal por 14 dias, receberam 100µg de PGF2α (Ciosin®) no sétimo dia e foram superovuladas, a partir do 12º dia, com 250UI de FSH (Folltopin-V®) em seis doses decrescentes. No dia da retirada do implante, as doadoras do G2 receberam 125mg de rbST (Boostin®) e foram cobertas por macho Santa Inês a cada 12 horas até o final do estro. No sexto dia após a primeira cobrição, foram avaliadas, por laparoscopia, a resposta superovulatória e a quantidade e a qualidade dos corpos lúteos. Após as avaliações, as colheitas embrionárias foram realizadas por laparotomia. A administração da rbST no protocolo de superovulação promoveu aumento significativo (P<0,05) no número de corpos lúteos do tipo I (9,00 x 5,28) e na qualidade embrionária (4,33 x 2,00).

Effects of flunixin meglumine, recombinant bovine somatotropin and/or human chorionic gonadotropin on pregnancy rates in Nelore cows

The objective was to compare pharmacological strategies aiming to inhibit prostaglandin F2 alpha (PGF(2α)) synthesis (flunixin meglumine; FM), stimulate growth of the conceptus (recombinant bovine somatotropin; bST) and progesterone (P(4)) synthesis (human chorionic gonadotropin; hCG), as well as their combinations, regarding their ability to improve pregnancy rates in beef cattle. Lactating Nelore cows (N = 975), 35 to 70 days postpartum, were synchronized and inseminated by timed artificial insemination (TAI) on Day 0. On Day 7, cattle were allocated into eight groups and received one of the following treatments: saline (S) on Days 7 and 16 (Group Control); S on Day 7 and FM on Day 16 (Group FM); bST on Day 7 and S on Day 16 (Group bST); bST on Day 7 and FM on Day 16 (Group bST + FM); hCG on Day 7 and S on Day 16 (Group hCG); hCG on Day 7 and FM on Day 16 (Group hCG + FM); bST and hCG on Day 7 and S on Day 16 (Group bST + hCG), or bST and hCG on Day 7 and FM on Day 16 (Group bST + hCG + FM). The aforementioned treatments were administered at the following doses: 2.2 mg/kg FM (Banamine®; Intervet Schering-Plough, Cotia, SP, Brazil), 500 mg bST (Boostin®; Intervet Schering-Plough), and 2500 IU hCG (Chorulon®; Intervet Schering-Plough). Pregnancy diagnosis was performed 40 days after TAI by transrectal ultrasonography. Pregnancy rates were not significantly different among treatments. However, there was a main effect of hCG treatment to increase pregnancy rates (63.0 vs. 55.4%; P = 0.001). Concentrations of P(4) did not differ significantly among groups on Day 7 or on Day 16. However, consistent with the higher pregnancy rates, hCG increased P(4) concentrations on Day 16 (10.6 vs. 9.6 ng/mL, respectively; P = 0.05). We concluded that hCG treatment 7 days after TAI improved pregnancy rates of lactating Nelore cows, possibly via a mechanism leading to induction of higher P(4) concentrations, or by reducing the luteolytic stimulus during maternal recognition of pregnancy.

Increased cleavage and blastocyst rate in ewes treated with bovine somatotropin 5 days before the end of progestin-based estrous synchronization

Treatment with bovine somatotropin (bST) during estrous synchronization increased fertility and prolificacy in sheep. In the present study, a single dose of bST 5 days before the end of progestin treatment improved cleavage and embryo development. Stage of estrous cycle was synchronized in ewes (n=32) with progestin and superovulation was induced by use of FSH. Five days before the end of progestin treatment, ewes were randomly assigned to two groups: bST group (n=16) received a depot injection of 125 mg of bST sc (Lactotropina, Elanco, México) and the control group (n=16) received saline solution. Estrous was detected with rams fitted with an apron every 2 h and estrous sheep were mated every 8 h whilst in estrous. Embryos were recovered on Day 7 post mating, assessed microscopically and fixed in 4% paraformaldehyde. Cell number in blastocysts was counted after Hoechst 33342 staining. Plasma concentrations of IGF-I, insulin and progesterone were determined in eight sheep per group from the day of bST treatment to the day of embryo recovery. Cleavage rate, percentage of transferable embryos (transferable embryos/cleaved) and percentage of embryos reaching the blastocyst stage (blastocyst/cleaved) were compared between groups by logistic regression. IGF-I, insulin and progesterone plasma concentrations were analyzed by ANOVA for repeated measurements and cell number by ANOVA. Cleavage rate was greater (P<0.01) in bST treatment group (86%) than in the control group (62%). Similarly, the proportion of embryos reaching the blastocyst stage (bST=68.7 vs control=42.5) and the number of cells per blastocyst (bST group 91.8±5.5 compared to control group 75±6) were greater (P<0.01) in the bST-treated sheep. Plasma concentrations of IGF-I and insulin were greater (P<0.01) in the bST-treated group. No changes were observed in progesterone concentrations (P=0.5). It is concluded that bST injection 5 days before progestin removal increases cleavage rate and the proportion of embryos that reach the blastocyst stage. These effects are associated with an increase in IGF-I and insulin concentrations.

Factors affecting fertilisation and early embryo quality in single- and superovulated dairy cattle

Data on fertilisation and embryo quality in dairy cattle are presented and the main factors responsible for the low fertility of single-ovulating lactating cows and embryo yield in superovulated dairy cattle are highlighted. During the past 50 years, the fertility in high-producing lactating dairy cattle has decreased as milk production increased. Recent data show conception rates to first service to be approximately 32% in lactating cows, whereas in heifers it has remained above 50%. Fertilisation does not seem to be the principal factor responsible for the low fertility in single-ovulating cows, because it has remained above 80%. Conversely, early embryonic development is impaired in high-producing dairy cows, as observed by most embryonic losses occurring during the first week after fertilisation. However, in superovulated dairy cattle, although fertilisation failure is more pronounced, averaging approximately 45%, the percentage of fertilised embryos viable at 1 week is quite high (>70%). Among the multifactorial causes of low fertility in lactating dairy cows, high feed intake associated with low concentrations of circulating steroids may contribute substantially to reduced embryo quality. Fertilisation failure in superovulated cattle may be a consequence of inappropriate gamete transport due to hormonal imbalances.

Serum progesterone concentration and conception rate of beef cows supplemented with ground corn after a fixed-time artificial insemination protocol

The effects of different levels of finely ground corn (FC) supplementation to grazing beef cows after fixed-time AI (TAI) on serum progesterone (P4) concentrations on day 7 and conception rates on day 28 after TAI were investigated. Three hundred and sixty-four lactating multiparous Brangus cows had follicular and luteal activity synchronized by treatment with estradiol benzoate (Estrogin; 2.0mg IM) and insertion of intra-vaginal P4 releasing device (CIDR) on day -11, followed by treatment with PGF2α (Lutalyse; 25mg IM) on day -4, CIDR and calf removal on day -2, and treatment with GnRH (Fertagyl; 100µg IM) TAI and calf return on day 0. On day 0, cows were randomly allotted in one of the following FC supplement treatments: G1 - 2kg/day from day 0 to 21; G2 - 2kg/day from day 0 to 7, and 6kg/day from day 8 to 21; G3 -6kg/day from day 0 to 7, and 2kg/day from day 8 to 21; and G4 -6kg/day from day 0 to 21. Blood samples were collected on day 7, and pregnancy was determined by ultrasonography indicating the presence of a fetus on day 28. Cows supplemented with 2kg/d of FC had higher serum concentration of P4 on day 7 than cows supplemented with 6kg/d (1.58 vs. 1.28ng/mL; P<0.01; SEM = 0.08). Cows from G4 had higher conception rates compared to G1 cows (58.4 vs. 41.9%, respectively; P<0.05). The level of supplemental energy intake after TAI is negatively associated with following serum P4 concentrations, but positively associated with conception rates of grazing beef cows.

Growth hormone co-treatment within a GnRH agonist long protocol in patients with poor ovarian response: a prospective, randomized, clinical trial

OBJECTIVE

The efficacy of growth hormone co-stimulation to long luteal GnRHa regimen in poor responders to COH for IVF was assessed.

METHODS

This prospective, randomized, clinical trial was performed in a private assisted reproduction center. The study involved 61 patients who responded poorly to high dose gonadotropin treatment in their first cycles in the same center. Study group of 31 patients were given growth hormone co-treatment, daily subcutaneous injection of 4 mg from day 21 of preceding cycle along with GnRHa, until the day of hCG. Control group of 30 patients received the same treatment protocol except the growth hormone cotreatment. Primary end-point of the study was the number of oocytes fertilized whereas the pregnancy rate was the secondary end-point.

RESULTS

Patients' demographic characteristics did not differ significantly between the two groups. 2PNs in growth hormone co-treatment group was significantly higher than the control group (4.4 +/- 1.8 vs 1.5 +/- 0.9, p < 0.001). Although more pregnancies and more clinical pregnancies with fetal heart beat were achieved in growth hormone group (12/31), compared to the control group (6/30), the difference did not reach to statistical significance.

CONCLUSION

Poor responder women undergoing repeated assisted reproduction treatment and co-stimulated with GH achieve more oocytes, higher fertilization rate if growth hormone started in the luteal phase of previous cycle, as compared with women of the same status treated with GnRHa long protocol. The study was unable to show that clinical pregnancy rate was increased significantly.

Progesterone regulates FGF10, MET, IGFBP1, and IGFBP3 in the endometrium of the ovine uterus

Progesterone (P4) is unequivocally required to maintain a uterine environment conducive to pregnancy. This study investigated the effects of P4 treatment on expression of selected growth factors (fibroblast growth factor 7 [FGF7], FGF10, hepatocyte growth factor [HGF], and insulin-like growth factors [IGF1 and IGF2]), their receptors (MET, FGFR2(IIIB), and IGF1R), and IGF binding proteins (IGFBPs) in the ovine uterus. Ewes received daily injections of corn oil vehicle (CO) or 25 mg of P4 in vehicle from 36 h after mating (Day 0) to hysterectomy on Day 9 or Day 12. Another group received P4 to Day 8 and 75 mg of mifepristone (RU486, a P4 receptor antagonist) from Day 8 through Day 12. Endometrial FGF10 mRNA levels increased between Day 9 and Day 12 and in response to P4 on Day 9 in CO-treated ewes, which had larger blastocysts, and were substantially reduced in P4+RU486-treated ewes, which had no blastocysts on Day 12. Endometrial FGF7 or HGF mRNA levels were not affected by day or reduced by RU486 treatment, but MET mRNA levels were higher in P4-treated ewes on Day 9 and Day 12. Levels of IGF1, IGF2, and IGF1R mRNA in the endometria were not affected by early P4 treatment. Although stromal IGFBPs were unaffected by P4, levels of IGFBP1 and IGFBP3 mRNA in uterine luminal epithelia were increased substantially between Day 9 and Day 12 of pregnancy in CO-treated ewes and on Day 9 in early P4-treated ewes. Therefore, FGF10, MET, IGFBP1, and IGFBP3 are P4-regulated factors within the endometrium of the ovine uterus that have potential effects on endometrial function and peri-implantation blastocyst growth and development.

Uterine and hepatic gene expression in relation to days postpartum, estrus, and pregnancy in postpartum dairy cows

The somatotropic axis consisting of growth hormone, the growth hormone receptor (GHR) insulin-like growth factor (IGF)-I, and IGF binding proteins changes with the stage of lactation and nutrition of the cow and may be 1 mechanism through which lactation and nutrition affect the establishment of pregnancy. The objective of this study was to quantify GHR, IGF-I, and IGF binding protein-2 (IGFBP-2) mRNA in liver and uterine endometrial tissue at 4 stages of lactation (40, 80, 120, and 160 days in milk) and around the time of artificial insemination. Estrus was synchronized with GnRH and PGF2alpha, and cows were inseminated 12 h after estrus. Uterine biopsies were collected immediately before the second injection of PGF2alpha (before estrus), at the initiation of standing estrus, and 4 d after estrus. Liver biopsies were collected once on 4 d after estrus. The abundance of GHR, IGF-I, and IGFBP-2 mRNA in liver and uterus was determined by real-time quantitative PCR. The amount of liver IGF-I mRNA was positively correlated with plasma IGF-I concentrations. Cows that became pregnant after AI had more GHR and IGFBP-2 mRNA in their liver than cows that did not become pregnant. There was no effect of DIM or pregnancy status on abundance of uterine mRNA; however, uterine GHR and IGF-I mRNA was most abundant at estrus. In summary, cows at different stages of lactation or with different pregnancy statuses had similar quantities of uterine mRNA. In contrast, liver quantities of mRNA differed relative to pregnancy status. These data provide evidence that liver indices of metabolic state may be indicative of pregnancy success.

A single dose of bovine somatotropin 5 days before the end of progestin-based estrous synchronization increases prolificacy in sheep

Bovine somatotropin (bST) enhances ovarian follicular and embryonic development in sheep and cattle. In the present study, the objective was to assess whether bST given 5 days before the end of progestin-based estrous synchronization improves prolificacy and lambing rate in sheep. Pelibuey ewes (n=92) exhibiting estrous cycles at regular intervals received an intravaginal sponge containing 45mg of FGA for 12 days. Five days before sponge withdrawal, ewes were treated with either 125mg of bST sc (bST group; n=47) or saline solution (control; n=45). After the sponge was removed, ewes were observed for estrus and subsequently mated twice. Lambing rate and prolificacy was determined at birth. Blood samples were taken from the time of treatment until day 15 after estrus in eight ewes from the bST group and nine from the control group. Concentrations of IGF-I were determined by immunoradiometric assay and progesterone by RIA. Treatment with bST increased (P<0.01) the proportion of ewes with more than one lamb (bST, 56% compared with control, 26%) and prolificacy (bST, 1.6 compared with control, 1.3). Treatment with bST increased (P<0.05) the lambing rate of multiparous (bST, 92% compared with control, 67%) but not in ewes at the first time they were mated (bST, 71% compared with control, 87%; P>0.05). IGF-I concentrations were greater (P<0.01) in ewes treated with bST than in control ewes from 2 days after treatment. Progesterone concentrations did not vary (P>0.05) between groups. It is concluded that a single dose of bST 5 days before progestin withdrawal increases lambing rate and prolificacy in sheep. These effects are associated with an increase in circulating concentrations of IGF-I.

Fertility of Lactating Dairy Cows Administered Recombinant Bovine Somatotropin During Heat Stress

Administration of recombinant bovine somatotropin (bST) to lactating dairy cows during heat stress increases milk yield, but it also can increase body temperature and may therefore compromise fertility. However, it is possible that bST treatment could increase fertility during heat stress because it has been reported to increase fertility in lactating cows. In addition, bST increases secretion of insulin-like growth factor-I (IGF-I) that promotes embryo survival. The purpose of this study was to determine effects of bST on reproductive function in lactating dairy cows during heat stress. The experiment was conducted in southern Georgia from July to November 2005 using lactating Holstein cows (n = 276 for reproductive traits). For first service timed artificial insemination (TAI), cows were presynchronized with 2 injections of PGF(2alpha) given 14 d apart followed by a modified Ovsynch protocol (GnRH and insemination at 72 h following PGF(2alpha) ). Pregnancy was diagnosed by using ultrasonography on d 29 and reconfirmed by palpation between d 45 and 80 post-TAI. Nonpregnant cows were resynchronized with the modified Ovsynch protocol and received a second TAI. Treatment with bST started 1 wk before the start of Ovsynch and continued at 2-wk intervals. Blood samples were collected from a subset of cows to determine IGF-I profiles immediately before the first bST injection, 1 wk later, and at d 35 of bST treatment. Rectal temperatures were assessed on d 29 of bST treatment. Pregnancy rates (d 45 to 80 post-TAI) did not differ between bST and control cows for first- (16.7 vs. 15.2%) or second-service TAI (14.8 vs. 17.2%). Plasma concentrations of IGF-I and milk yield were greater for bST-treated cows following the initiation of bST treatment and bST increased rectal and vaginal temperatures. Body condition score was less for bST-treated cows. In conclusion, treatment with bST during heat stress increased IGF-I concentrations, milk yield over time, and rectal and vaginal temperatures without affecting first- or second-service pregnancy rates. Thus, at least under certain housing conditions, bST can be used to improve milk yield during heat stress without compromising fertility.

Follicle Ablation Improves the Ovarian Response and the Number of Collected Embryos in Superovulated Cows During the Early Stages of Lactation

A field study was designed to compare ovarian response and embryo yield in cows during early lactation when gonadotropin administration followed one of four treatments. In group 1A (n = 19) and 1B (n = 9), the estrouses were synchronized by two prostaglandin F2alpha (PG) injections given 11 days apart, and starting from day 9 of the synchronized cycle superovulation was conducted with eight decreasing dose of FSH. In group 1B, ablation of all follicles >3 mm was carried out on day 8. In group 2A and 2B (each n = 9), a progesterone plus oestradiol intravaginal device (PRID) was inserted for 11 days and gonadotropin administration started on day 9, while cows from group 2B had a follicle ablation on day 8. In all groups, two PG injections were given along with the sixth and the seventh dose of FSH, and the cows were twice inseminated 12 and 24 h after estrus detection. Embryos were collected on day 7. In cumulative results from aspirated and non-aspirated cows, follicular ablation significantly improved: the ovarian response (10 +/- 1.23 vs 6.69 +/- 0.60 corpora lutea per donor), the mean collected embryos (6.57 +/- 0.94 vs 2.46 +/- 0.53) and the mean transferable embryos (4.43 +/- 0.89 vs 2.18 +/- 0.47). Group 1B and 2B cows had better ovarian response than 1A (6.44 +/- 0.81, 12.25 +/- 4.11 and 9.44 +/- 0.93, for groups 1A, 1B and 2B, respectively, p < 0.05). Similarly, from groups 1B and 2B more (p < 0.05) embryos were collected in comparison with their respective group, while the mean transferable embryos from group 2B (5.22 +/- 1.13) was greater (p < 0.05) than that of group 1A (1.67 +/- 0.35), and tented to be greater than those of groups 2A (3.44 +/- 1.19, p = 0.062) and 1B (3.00 +/- 1.78, p = 0.066). The highest (p < 0.05) transferable embryo collection rate was recorded in group 2B (55.29%), followed by that of group 1B (41.33%). In summary, early in lactation, an acceptable number of transferable embryos can be collected from high producing dairy cows, when follicle ablation prior to superovulation is combined with progesterone and oestradiol administration.

Insulin-like growth factor-I promotes resistance of bovine preimplantation embryos to heat shock through actions independent of its anti-apoptotic actions requiring PI3K signaling

For the bovine preimplantation embryo, insulin-like growth factor-I (IGF-I) is a survival factor that blocks the induction of apoptosis and reduces the decrease in development caused by heat shock. The first objective was to determine the signaling pathways whereby IGF-I acts to increase embryo cell number while inhibiting heat-shock induced apoptosis. Exposure of embryos to heat shock reduced cell number and increased percent apoptosis, but IGF-I increased cell number and blocked induction of apoptosis caused by heat shock. Actions of IGF-I to increase cell number were blocked by treatment with the mitogen activated protein kinase kinase (MAPKK) inhibitor PD 98059 whereas the phosphatidylinositol 3-kinase (PI3K) inhibitor LY 294002 had no effect. Conversely, LY 294002 but not PD 98059 blocked actions of IGF-I to inhibit induction of apoptosis caused by heat shock. The second objective was to determine whether IGF-I blocks effects of heat shock on development to the blastocyst stage by preventing apoptosis. Culture of embryos with IGF-I was effective in blocking the reduction in blastocyst development caused by heat shock-this action occurred even in the presence of LY 294002. Addition of another inhibitor of apoptosis, the caspase-3 inhibitor z-DEVD-fmk, did not mimic the protective effects of IGF-I on blastocyst development. Surprisingly, IGF-I was not effective in blocking the reduction in blastocyst development caused by heat shock when cultured with z-DEVD-fmk. In conclusion, the anti-apoptotic actions of IGF-I require PI3K signaling while actions to promote proliferation require MAPKK signaling. Moreover, actions of IGF-I to allow heat-shocked embryos to continue development to the blastocyst stage are independent of its anti-apoptotic effects.

Pregnancy, Bovine Somatotropin, and Dietary n-3 Fatty Acids in Lactating Dairy Cows: I. Ovarian, Conceptus, and Growth Hormone–Insulin-Like Growth Factor System Responses

The objective was to examine effects of bovine somatotropin (bST), pregnancy, and dietary fatty acids on reproductive responses in lactating dairy cows. Beginning at approximately 17 d in milk (DIM), a comparison was made of isoenergetic diets comprising supplementary lipids of whole cottonseed vs. calcium salts of fish oil enriched lipid (FO). Ovulation was synchronized in cows with a presynchronization plus Ovsynch protocol, and cows were inseminated artificially by appointment or not inseminated (d 0 = time of synchronized ovulation; 77 +/- 12 DIM). On d 0 and 11, cows received bST (500 mg) or no bST. All cows were slaughtered on d 17. Number of cows in each group was as follows: control diet had 5 bST-treated cyclic (bST-C), 5 non-bST-treated cyclic (no bST-C), 4 bST-treated pregnant (bST-P), and 5 non-bST-treated pregnant (no bST-P) cows; and cyclic cows fed FO diet had 4 bST-treated (bST-FO) and 5 non-bST-treated cyclic (no bST-FO-C) cows. Feeding FO increased milk production, number of class 1 follicles (2 to 5 mm), and decreased insulin during the period before d 0 compared with control-fed cows. The bST increased milk production, pregnancy rate [83% (5/6) vs. 40% (4/10)], conceptus length (45 vs. 34 cm), and interferon-tau in the uterine luminal flushings (9.4 vs. 5.3 microg) with no effect on interferon-tau mRNA concentration in the conceptus. Treatment with bST increased plasma growth hormone (GH) and insulin-like growth factor (IGF)-I. Among control-fed cows (cyclic and pregnant), bST decreased progesterone concentration in plasma. Cows fed FO had less plasma insulin than control-fed cyclic cows, and FO altered the plasma GH (bST-FO > bST-C) and IGF-I (bST-C > bST-FO-C) responses to bST injections. Endometrial IGF-I mRNA was reduced in pregnant cows and tended to decrease in those fed FO. The IGF-II mRNA was increased in the endometrium of pregnant and bST-treated cows fed the control diet. Cows fed FO had increased concentrations of IGF-II mRNA, when bST was not injected. The insulin-like growth factor binding protein-2 (IGFBP-2) mRNA was increased in bST-P cows, whereas bST decreased the IGFBP-2 mRNA in all cyclic cows. In summary, bST and FO seemed to modulate reproductive responses that may be beneficial to the developing conceptus and pregnancy rate.

Strategies for improving fertility in the modern dairy cow

The high producing dairy cow of the 21st century is subfertile during lactation. Our objectives are to characterize physiological periods limiting reproductive performance and to describe integrated management strategies to improve pregnancy rates. Ovarian recrudescence with normal re-occurring estrous cycles and restoration of fertility to first service are associated with a reduced occurrence of periparturient metabolic and reproductive disorders. Marked negative changes in energy balance and reduced immunocompetence influence gonadotropic and metabolic hormones. Induced ovarian inactivity was associated with enhanced uterine involution. Post-partum health and reproductive performance were improved when by-pass lipids enriched in polyunsaturated fatty acids were fed in the pre- and post-partum periods. Pharmaceutical control of follicle, CL, and uterine function with PGF, GnRH and intravaginal progesterone releasing inserts, has permitted development of more optimal timed-insemination programs for first service. Likewise, resynchronization of nonpregnant cows coupled with the use of ultrasound for early pregnancy diagnosis provides the opportunity for a second timed-insemination within 3 days of a nonpregnant diagnosis. Bovine somatotropin (bST) increases embryo development and embryo survival when coupled with a timed-insemination program or cows detected in estrus. Presence of a conceptus alters endometrial expression of genes and proteins in response to bST and nutraceuticals (i.e., unsaturated fatty acids such as eicosapentaenoic and docosahexaenoic acid in by-pass lipids) to improve pregnancy rates. Postovulatory increases in progesterone may enhance pregnancy rates in targeted populations of lactating dairy cows, but timing and magnitude of the progesterone increases are pharmaceutically dependent.

The usefulness of a single measurement of insulin-like growth factor-1 as a predictor of embryo yield and pregnancy rates in a bovine MOET program

The objective was to determine if a single measurement of plasma insulin-like growth factor-1 (IGF-1) could predict the number of viable embryos obtained from donors and the likelihood of pregnancy in recipients in multiple ovulation and embryo transfer (MOET) programs in cattle. The embryo yields from 101 embryo recoveries were examined in maiden Holstein heifers (n=75) and multiparous Holstein cows (lactating cows n=20, dry cows n=6). Donors were super stimulated with FSH and embryo recovery was done non-surgically 7 days after artificial insemination. Embryos were classified according to the IETS criteria. Pregnancy rates in 100 maiden Holstein heifer recipients were analysed. Recipients were on day 7+/-1 of the estrous cycle at transfer. Pregnancy diagnosis was carried out at day 30 (PD 30) and rechecked at day 60 (PD 60) after transfer. Blood samples from coccygeal vessels taken at the time of embryo recovery (donors) and transfer (recipients) were analysed for IGF-1, insulin, beta-hydroxybutyrate (beta-OHB), non-esterified fatty acids (NEFA), urea and cholesterol. There was a negative correlation between the number of viable embryos and insulin (r=-0.33, P=0.025) in donor heifers. In donor cows, the number of viable embryos was correlated with IGF-1 (r=0.43, P=0.028) and cholesterol (r=-0.43, P=0.027). In recipients, PD30 and PD 60 were not affected by any of the circulating parameters analysed. Insulin, IGF-1 and cholesterol only explained 8.9, 13.9 and 15.8% of the variation in the production of viable embryos, respectively. Several factors affect MOET programs and under the circumstances of the present study the usefulness of hormonal and metabolic profiles as predictors of the outcome of this biotechnology was limited.

Improvement of delivery and live birth rates after ICSI in women aged >40 years by ovarian co-stimulation with growth hormone

BACKGROUND

Growth hormone (GH) is required for ovarian follicular development, and its administration during ovarian stimulation improves pregnancy rate in cow and sheep. Data on the use of exogenous GH in human assisted reproduction treatment are inconsistent. This prospective randomized study evaluates the usefulness of GH administration in women of >40 years undergoing ovarian stimulation for assisted reproduction treatment.

METHODS

One hundred women of >40 years undergoing assisted reproduction treatment were randomized between a GH treatment group and a placebo group. Assisted reproduction treatment outcomes were evaluated.

RESULTS

In patients of the GH treatment group, a similar number of oocytes, embryos and pregnancies was achieved as compared with the placebo group. However, the patients treated with GH suffered fewer pregnancy losses, resulting in higher delivery and live birth rates. These patients also showed higher peak serum estradiol concentration and higher concentrations of GH and estradiol in pre-ovulatory follicular fluid as compared with the placebo group.

CONCLUSIONS

Administration of GH during ovarian stimulation alleviates age-related decrease in assisted reproduction treatment efficiency. This effect appears to be mainly due to an improvement of oocyte developmental potential, but GH action on the uterus cannot be excluded.

Pré-tratamento com somatotropina bovina (rbST) na superovulação de doadoras da raça Holandesa

Estudou-se o efeito da somatotropina bovina recombinante (rbST) sobre o número e qualidade dos embriões de 40 vacas da raça Holandesa, distribuídas aleatoriamente em três grupos: controle (GI, n=15), tratadas com 250mg de rbST (GII, n=11) e tratadas com 500mg de rbST (GIII, n=14) no sexto dia do ciclo estral. No décimo dia após o estro, as doadoras foram submetidas ao tratamento superovulatório com 360mg de hormônio folículo estimulante (FSH) em doses decrescentes, duas vezes ao dia, com intervalos de 12 horas. Juntamente com a sétima aplicação de FSH foram administrados 0,5mg de cloprostenol (análogo da PGF2alfa) e as doadoras inseminadas artificialmente 12, 20 e 28 horas após o início da manifestação de estro. Os embriões foram coletados, não cirurgicamente, no sétimo dia após a primeira inseminação. A administração de 250 ou 500mg de rbST aumentou (P<0,05) o percentual de embriões viáveis e não alterou a taxa de gestação das receptoras.

Insulin-like Growth Factor-I as a Survival Factor for the Bovine Preimplantation Embryo Exposed to Heat Shock1

Insulin-like growth factor-I (IGF-I) is a survival factor for preimplantation mammalian embryos exposed to stress. One stress that compromises preimplantation embryonic development is elevated temperature (i.e., heat shock). Using bovine embryos produced in vitro as a model, it was hypothesized that IGF-I would protect preimplantation embryos by reducing the effects of heat shock on total cell number, the proportion of blastomeres that undergo apoptosis, and the percentage of embryos developing to the blastocyst stage. In experiment 1, embryos were cultured with or without IGF-I; on Day 5 after insemination, embryos >or=16 cells were cultured at 38.5 degrees C for 24 h or were subjected to 41 degrees C for 9 h followed by 38.5 degrees C for 15 h. Heat shock reduced the total cell number at 24 h after initiation of heat shock and increased the percentage of blastomeres that were apoptotic. Effects of heat shock were less for IGF-I-treated embryos. Experiment 2 was conducted similarly except that embryos were allowed to develop to Day 8 after insemination. The percentage reduction in blastocyst development for heat-shocked embryos compared with those maintained at 38.5 degrees C was less for embryos cultured with IGF-I than for control embryos. Heat shock reduced the total cell number in blastocysts and increased the percentage of blastomeres that were apoptotic, whereas IGF-I-treated embryos had increased total cell number and a reduced percentage of apoptosis. Taken together, these results demonstrate that IGF-I can serve as a survival factor for preimplantation bovine embryos exposed to heat shock by reducing the effects of heat shock on development and apoptosis.

Pregnancy and Bovine Somatotropin in Nonlactating Dairy Cows: I. Ovarian, Conceptus, and Insulin-Like Growth Factor System Responses

Nonlactating dairy cows were used to examine effects of bovine somatotropin (bST) on components of the insulin-like growth factor (IGF) system. Estrus was synchronized in cows with a Presynch + Ovsynch protocol and timed AI (TAI; n = 55) or not TAI (cycling, C; n = 23) on d 0 (time of synchronized ovulation). On d 0 and 11, cows received bST (500 mg) or no bST, and were sacrificed on d 17. Pregnancy rates were less in bST cows (27.2%, 9 of 33) than in controls (63.6%; 14 of 22). In contrast, conceptuses were larger in bST-treated cows (39.2 +/- 4.8 cm) than in controls (20 +/- 4.3 cm). Total interferon-tau in uterine luminal flushings (ULF) was greater in bST-treated cows (7.15 > 2.36 microg). Number of class 2 follicles (6 to 9 mm) was less in bST-C cows on d 7 and 16. On d 17, corpus luteum (CL) weight tended to be greater in bST-treated cows. Concentrations of progesterone were greater after d 10 in C than in pregnant (P) cows. In the ULF, IGF-binding protein-3 was greater in bST-P cows than in pregnant cows. A tendency for an increase in IGF-I hormone concentrations in the ULF was detected on d 17 in bST-treated and cyclic cows. Endometrial mRNA for IGF-I, IGF-II, IGFBP-2, and IGFBP-3 increased in bST-C, but not in bST-P cows. Treatment with bST increased plasma concentrations of insulin, IGF-I, and growth hormone (GH). In conclusion, bST may have hyperstimulated plasma IGF-I and insulin to cause asynchrony between conceptus and uterus that was detrimental to pregnancy.

The effect of embryonic death rates in cattle on the efficacy of estrus synchronization programs

Reproductive failure in inseminated cattle results from poor fertilization and embryo survival. Recent studies utilizing dairy and beef cattle indicate that fertilization rates are higher for nulliparous dairy and beef heifers and nonlactating beef cows than lactating beef and dairy cows and nonlactating dairy cows. Several factors affect fertilization rates, but the greatest impact was observed for high producing cows under heat stress, when fertilization was only 55%. Once fertilization has occurred, the fate of a successful pregnancy is then determined by the survival of the embryo and fetus. Losses of pregnancy are characterized by early embryonic death, which occurs prior to the period of corpus luteum (CL) maintenance in the cow at days 15-17 of the cycle, and late embryonic death, which occurs from CL maintenance to the end of the differentiation stage, at approximately 42 days of gestation. After 50 days of gestation, pregnancy losses are less frequent and characterize fetal death. Most pregnancy losses occur prior to the period of maintenance of the CL, but in high producing lactating dairy cattle, substantial losses continue to occur up to 42-56 days after insemination. Several factors affect pregnancy losses in cattle, such as compromised oocytes, which result in poorly developed embryos incapable of cross-talking with the endometrial epithelial cells, to inadequate uterine environment and infectious agents resulting in death of the embryo from undernourishment. Recently, studies have indicated that anovulation/anestrous, the metabolic status of the animal, some dietary ingredients, as well as occurrence of diseases, predispose the cow to experience embryonic and fetal death. Although some insemination protocols might impact embryo survival, when timed AI has been implemented properly, it has not influenced embryonic or fetal death in cattle. Improvements in reproductive programs in the future will have to focus on enhancing fertilization rates and minimizing embryonic losses to optimize conception rates in dairy and beef cattle.

Improvement of the Developmental Capacity of Oocytes from Prepubertal Cattle by Intraovarian Insulin-Like Growth Factor-I Application1

The developmental potential of oocytes from prepubertal cattle is decreased, compared with those from their adult counterparts. The aim of the present study was to improve the developmental capacity of oocytes from prepubertal cattle by either systemic application of recombinant bovine somatotropin (rbST) or intraovarian injection of insulin-like growth factor-I (IGF-I). Blastocyst yields and the mRNA expression pattern (relative abundance, RA) of three putative marker genes (i.e., glucose transporter-1, Glut-1; eukaryotic translation initiation factor-1A, eIF1A, and upstream binding factor, UBF) were selected as criteria to determine the success of the treatments. At 6-7 mo of age, 30 healthy Holstein calves were randomly assigned to three experimental groups. The first group served as control and received an intraovarian injection of 0.6 ml acetic acid. The second group received a single s.c. injection of 500 mg of rbST. The third group received an intraovarian injection of 6 microg recombinant human IGF-I. During the following 2 wk, follicles were aspirated four times via transvaginal ultrasound-guided technology. All animals were i.m. injected with 60 mg FSH 48 h prior to each aspiration. The treatments were repeated with the same animals at 9-10, 11-12, and 14-15 mo of age. For comparison, five adult cows were each i.m. injected with 100 mg FSH and underwent oocyte retrieval. The proportion of oocytes considered to be developmentally competent was higher in cows than calves (65% vs. 58%, 50%, 52%) for the control, rbST, and IGF-I groups, respectively. The rate of blastocysts was similar in IGF-I-treated calves and cows (28% and 25%) and was higher (P </= 0.05) than in the controls and the rbST group (11% and 16%). The RA for Glut-1 was lower (P </= 0.05) in two- to four- cell embryos from calves, compared with cows. At the 8- to 16- cell stage, Glut-1 RA was similar in IGF-I-treated calves and cows. The RA for eIF1A was higher (P </= 0.05) in 8- to 16-cell embryos derived from cows than those from the control group. Results show that IGF-I intraovarian injection increased blastocyst yields and mRNA expression of Glut-1 and eIF1A to levels found in embryos produced from adult cows. This treatment may at least partially overcome the developmental deficiency of oocytes derived from calves and could be a step forward toward the use of prepubertal animals in breeding programs aimed at shortening the generation interval.

Effect of bST and Reproductive Management on Reproductive Performance of Holstein Dairy Cows

The objective was to determine the effects of bovine somatotropin (bST) and two artificial insemination (AI) protocols on reproductive performance of Holstein cows. Lactating cows (n = 840) were assigned at 37 d in milk (DIM) to one of four treatments in a 2 x 2 factorial arrangement. Treatments consisted of either bST (500 mg/14 d) starting at 63 +/- 3 DIM or no bST (control), with cows either submitted for timed AI following a synchronized ovulation (Ovsynch) protocol or assigned to receive AI based on estrus detection (ED). Two injections of PGF2, at 37 +/- 3 and 51 +/- 3 DIM were used to presynchronize estrous cycles. Cows then received an injection of GnRH at 63 +/- 3 DIM, followed 7.5 d later by PGF2. Cows assigned to ED treatments were inseminated after observed estrus during a 7-d period. Cows in Ovsynch treatments received a second GnRH injection 48 h after the last PGF2alpha and received timed AI 16 to 18 h later. Pregnancy was diagnosed by ultrasound at 31 d after AI and confirmed 14 d later. Frequency of anovulation (18.5%) at 63 DIM was similar across treatments, but proportions of anovulatory cows decreased quadratically as body condition at 70 DIM increased from 2.25 to 3.75. Estrus detection rate after PGF2alpha tended to be lower in multiparous cows receiving bST, and bST reduced returns to estrus in nonpregnant cows. Conception rates were higher in cows receiving AI after ED and bST improved conception rates to first AI in cyclic cows by reducing embryonic mortality. Pregnancy loss was similar for cows inseminated following ED or the Ovsynch protocol. There was a positive impact of bST on fertility of cyclic cows inseminated at fixed time or at detected estrus, but effective resynchronization protocols are needed to optimize reinsemination of non-pregnant bST-treated cows.

Towards an embryocentric world: the current and potential uses of embryo technologies in dairy production

Structural features of the dairy industry make it well situated to use embryo technologies as tools for enhancing the genetic merit of dairy cattle and improving fertility. Technologies dependent upon embryo transfer have the potential to increase the efficiency of quantitative genetic selection as well as marker-assisted selection, simplify cross-breeding and germplasm conservation procedures and allow incorporation of transgenes into dairy cattle. In addition, embryo technologies may prove useful in improving fertility in infertile populations of lactating cows. The realisation of the promise of embryo technologies has been constrained by suboptimal efficiency in the production of embryos, alterations in embryonic and fetal survival and development associated with in vitro embryo production and cloning, as well as other technical and societal concerns. Solutions to many of these constraints are possible and the use of embryo technologies in both nucleus and commercial herds is likely to increase. Eventually, embryo transfer may compete with artificial insemination as a dominant method for establishing pregnancies in dairy cattle.

Actions of Tumor Necrosis Factor-α on Oocyte Maturation and Embryonic Development in Cattle1

PROBLEM

Infertility can accompany mastitis in cattle. Involvement of tumor necrosis factor-alpha (TNF-alpha) in this phenomenon is suggested by observations that circulating concentrations of TNF-alpha are elevated after intramammary infection or infusion of endotoxin. It was hypothesized that (1) TNF-alpha acts on the oocyte during maturation to decrease the percent of oocytes that cleave and develop following fertilization; (2) exposure of embryos to TNF-alpha after fertilization reduces development to the blastocyst stage; and (3) TNF-alpha increases the proportion of blastomeres that undergo apoptosis in a stage-of-development dependent manner.

METHOD OF STUDY

In one experiment, oocytes were matured with various concentrations of TNF-alpha and then fertilized and cultured without TNF-alpha. In another study, embryos were cultured with TNF-alpha for 8 days beginning after fertilization. Finally, embryos were collected at the two or four-cell stage (at 28-30 hr after insemination) or when > or = 9-cells (at day 4 after insemination) and cultured +/- TNF-alpha for 24 hr. The proportion of blastomeres undergoing apoptosis was then determined by the TUNEL procedure.

RESULTS

Addition of TNF-alpha to maturation medium did not affect the proportion of oocytes that cleaved. However, the percent of oocytes that developed to the blastocyst stage at day 8 after insemination was reduced (P = 0.05) at all TNF-alpha concentrations tested (0.1-100 ng/mL). When added during embryo culture, there was no significant effect of TNF-alpha on the proportion of oocytes that became blastocysts. In addition, TNF-alpha did not induce apoptosis in two and four-cell embryos. For embryos > or = 9-cells, however, 10 and 100 ng/mL TNF-alpha increased (P < 0.05) the percent of blastomeres labeling as TUNEL-positive.

CONCLUSION

TNF-alpha can have deleterious actions on oocyte maturation that compromise development of the resultant embryo. While exposure of fertilized embryos to TNF-alpha did not inhibit development to the blastocyst stage, TNF-alpha increased the percentage of blastomeres undergoing apoptosis when exposure occurred for embryos > or = 9-cells. Increased blastomere apoptosis could conceivably compromise subsequent embryo survival.

Stage-Specific Effect of Growth Hormone on Developmental Competence of Bovine Embryos Produced In-Vitro

Many efforts have been made to develop effective culture conditions for the production of bovine blastocysts. Growth hormone (GH) and glucose are known to affect in vitro embryo development. To improve in vitro culture conditions, the culture medium containing fetal calf serum (FCS) or bovine serum albumin (BSA) was supplemented with GH at various periods of development, and the effects of GH on the rate of development and the quality of the blastocysts were studied. Then, starting at the morula stage, the effect of glucose and GH on the rate of development was studied. In all experimental periods, FCS was more effective than BSA at improving the development rate and increasing the cell number of blastocysts. Adding GH to the culture medium between 18 and 48 h after fertilization (1-8 cell stage embryo) did not affect either the rate of blastulation or the cell number regardless of the serum protein (FCS or BSA). From 48 to 120 h after fertilization (5-cell to morula stage) GH increased the cell number of the blastocysts in the presence of BSA, but not in the presence of FCS. From 120 to 192 h after fertilization (morula to blastocyst stage), GH improved the developmental rate and cell number in the presence of FCS, although there was no significant difference when BSA was used instead of FCS as the serum protein. When cows were implanted with blastocysts developed in the presence of GH from the morula stage, their pregnancy rate did not differ from that of the control. Increasing the glucose concentration in the medium from 1.5 mM to 3 mM starting at the morula stage (120 h after fertilization) slightly decreased the rate of development, but on the other hand, decreasing the glucose concentration to 0 mM did not affect either the rate of development or the cell number. Also, then GH had no effect on the developmental rate or the cell number in the absence of glucose. In conclusion, when the medium was supplemented with serum, GH improved embryo development from the morula stage, but an increased concentration of glucose decreased embryo development. Furthermore, GH did not improve the pregnancy rate of blastocysts developed in vitro.

Strategies to optimize reproductive efficiency by regulation of ovarian function

Pregnancy rate to the Ovsynch protocol can be improved if cows are presynchronized (i.e., two PGF(2alpha) injections given 14 days apart and the second injection of PGF(2alpha) given 12 days prior to the first GnRH of the Ovsynch program) so that a greater proportion of cows during the Ovsynch protocol ovulate to the first GnRH injection and have a CL at PGF(2alpha) injection. Pregnancy rates were normal in anestrous cows (39.6%) if they ovulated to both injections of GnRH. Estradiol cypionate (ECP) can be used to replace GnRH to induce ovulation as a modification of the Presync-Ovsynch program (i.e., Presync-Heatsynch). Pregnancy rates after TI were 37.1+/-5.8% for Presync-Ovsynch compared to 35.1+5.0% for Presync-Heatsynch. Use of ECP to induce ovulation was an alternative to GnRH in which greater uterine tone, ease of insemination and occurrence of estrus, improved acceptance by inseminators. A GnRH agonist (Deslorelin; 750 microg) implant inserted at 48 h after injection of PGF(2alpha), as a component of the Ovsynch protocol, induced ovulation, development of a normal CL and delayed follicular growth until 24 d after implant insertion. Utilization of Deslorelin implants (450 microg and 750 microg) to induce ovulation compared to GnRH (100 microg) within the Ovsynch protocol resulted in 27 d pregnancy rates (GnRH 100 microg, 39%; Deslorelin implants 450 microg, 40% and 750 microg, 27.5%) with 12.7%, 5.0% and 9.5% embryonic losses by 41 d of pregnancy, respectively. Induction of an accessory CL with injection of hCG on day 5 after insemination improved conception rates by 7.1%. Bovine somatotrophin injected at first insemination following a Presync-Ovsynch program in cycling-lactating dairy cows increased 74 days pregnancy rates (57.1%>42.6%).